Accelerometers have become multi-market devices due to cost-down using MEMS technology. MEMS accelerometers may be found in mobile phones, cars and game-controls. All commercial accelerometers are based on a tiny mass-spring system of which the displacement of the mass is proportional to the acceleration. To detect the displacement electronically, a capacitive read-out is the most common. Preferably, accelerometers are implemented as Micro-Electro-Mechanical Systems, also known as (MEMS) systems. Micro-Electro-Mechanical Systems may be denoted as the technology of the very small members, and merges at the nano-scale into nano-electromechanical systems (NEMS) and nanotechnology. MEMS may be made up of components between 1 μm (micrometer) to 100 μm (micrometer) in size and MEMS devices may generally range in size from 20 μm (micrometer) to 1 mm (millimeter).
Several operational areas are found. For measuring small accelerations in car stability programs and precise controllers in gaming applications, a highly linear response in the range from 0 to 2 g is needed.
In the following, the basic accelerator technology is explained. Consider a mass M on a spring with spring constant k. The force F on the mass due to an acceleration a is given byF=M·a. 
On the other hand, the force to exert the spring by a distance dx is given by the relationF=k·dx 
with k the spring constant. These two forces are in balance in (quasi) static situations because the mechanical inertia of the mass puts a force on the spring resulting in
  dx  =            M      k        ·          a      .      
So, the excursion dx of the mass is linearly dependent on the applied acceleration a. The relation is determined by the ratio M/k. The displacement of a mass may be measured capacitively by placing two capacitor plates on the two sides of the mass.
As shown in FIG. 1, between a first electrode 101 and a movable element 103 a first capacitor 104 may be represented and between a second electrode 102 and the movable element 103 a second capacitor 105 may be represented. As shown in FIG. 1, due to a movement of the movable element 103 along the main moving direction 110, the distance between the second electrode 102 and the movable element 103 may increase and the distance between the a second electrode 102 and the movable element 103 may decrease when the movable element 103 moves to the left, for instance.
To understand the relation of mechanical motion to a change in capacitance, the approximation for a parallel plate capacitor without fringing effects is sufficient:
  C  =            ɛ      ⁢                          ⁢      A        d  
with C the capacitance, A the surface e.g. of the capacitor plates or capacitor electrodes, d the gap thickness and ε the permittivity of the material in the gap. By example of parameter change, an increase in the gap thickness may give a decrease in the electrical capacitance.
U.S. Pat. No. 5,345,824 describes an accelerometer comprising a micro fabricated acceleration sensor and monolithically fabricated signal conditioning circuitry. The sensor comprises a differential capacitor arrangement formed by a pair of capacitors. Each capacitor comprises two electrodes, one of which it shares electrically in common with the other capacitor. One of the electrodes (e.g., the common electrode) is movable and one of the electrodes is stationary in response to applied acceleration. The electrodes are all formed of polysilicon members suspended above a silicon substrate. Each of the capacitors is formed of a plurality of pairs of electrode segments electrically connected in parallel and, in the case of the movable electrodes, mechanically connected to move in unison. When the substrate is accelerated, the movable electrodes move such that the capacitance of one of the capacitors increases, while that of the other capacitor decreases. The two capacitors are connected to signal conditioning circuitry, which converts this differential capacitance into a corresponding voltage.
U.S. Pat. No. 6,199,874 describes a micromechanical capacitive accelerometer from a single silicon wafer. The accelerometer may comprise a signal-conditioned accelerometer wherein signal-conditioning circuitry is provided on the same wafer from which the accelerometer is formed, and VLSI electronics may be integrated on the same wafer from which the accelerometer is formed. The micromechanical capacitive accelerometer can be used for airbag deployment, active suspension control, active steering control, anti-lock braking, and other control systems requiring accelerometers having high sensitivity, accuracy and resistance to out of plane forces.
US 2005/0132805 A1 describes an accelerometer capable of compensating initial capacitance. In the accelerometer, support beams are extended from a beam-fixing section to elastically support both ends of a horizontally movable floating mass. Movable electrodes are extended outward from both sides of the mass to a predetermined length. Fixed electrodes are extended from electrode-fixing sections to a predetermined length, and alternate with the movable electrodes with a predetermined gap. Compensation electrode sections displace the mass in a moving direction of the mass to equalize an initial capacitance between the movable and fixed electrodes at one side with that between the movable and fixed electrodes at the other side. The invention can simply displace the mass compensation electrodes to equalize initial capacitances at the both ends.
US 2006/272414 A1 discloses moveable microstructures comprising in-plane capacitive micro-accelerometers, with sub-micro-gravity resolution and high sensitivity. The microstructures are fabricated in thick silicon-on-insulator (SOI) substrates or silicon substrates using a two-mask fully-dry release process that provides large seismic mass, reduced capacitive gaps, and reduced in-plane stiffness. An AC signal is injected onto the proof mass or substrate.